Patent GB-560928-A (GB)
Title: Improvements in or relating to electrical systems for determining or transmitting a variable magnitude
IPC: G04F8/00
Filed: 1941-09-03
Abstract: 560,928. Electric signalling and controlling. WALTON, G. W. Sept. 3, 1941, No. 11290. [Class 40 (i)] [Also in Groups XXIX and XL] In systems of the kind in which the value of a variable is represented by the position of a signal impulse in a time period, the placing of the impulse is controlled jointly by two or more devices which measure the variable in accordance with different scales. Such impulses may be produced in accordance with the positions of controlling and controlled members and any difference of phase may cause a hydraulic motor to keep the controlled object in conformity with the controlling member. In another arrangement the position of the impulse in the time period is measured in accordance with two or more different scales so that the position is expressed with great accuracy by the position of the beams of two or more cathode-ray tubes. The invention can be applied to the simultaneous control of a number of widely separated guns from a single instrument at an observation post. Placing signal impulse in accordance with measured value. As shown in Fig. 1, a nut 21 is made to traverse a distance D by rotating a shaft 25 which is geared to a shaft W2 which in turn is geared to a shaft W1. The position of the nut is then represented on different scales by the angles through which these shafts have been turned. Each shaft carries the moving element of a phase shifting transformer A1 ... A3 and assuming both gear ratios to be 100, the primary windings of these transformers are fed with currents of frequencies f, 100f and 10,000f respectively derived from a source 26 and harmonic-producers M1, M2, Fig. 2. The twophase secondaries of these transformers are connected to the deflector electrodes of cathoderay switches having targets in the form of radial wires 28. The cathode beams are thus rotated and make contact with the targets once per revolution, the instant at which contact takes place depending on the phase of the deflecting voltages and these in turn depending on the angular position of the shafts W1, W2 and 25. The tubes are associated as shown in Fig. 4, tubes T2 and T3 being normally biassed to cut-off. When T1 passes an impulse, however, T2 is momentarily rendered effective and when its beam strikes the target it renders T3 effective, an impulse being sent to line 29 when the beam strikes the target in T3. The position of the impulse is thus dependent on the phases of the deflecting voltages in all three tubes. Controlling cathode-ray indicator by signal impulse. The signal impulse and an alternating current of the same frequency and phase as the original source at the sending point are received over a line 27, Fig. 5, and are separated in a device 37. The alternating current is used to provide two-phase currents for rotating the beams in a number of cathode-ray tubes at different speeds, e.g. at #, 100# and 10,000# and the signal impulses are fed in parallel to electrodes of the tubes so as to modify the beam and so cause a characteristic appearance on the fluorescent end of the tube, e.g. a luminous or dark spot or a swelling or diminution of a normal ring, at a point corresponding to the phase of the impulse. Comparison of positions of controlling and controlled object. The position of the controlled object is represented by the position of an impulse in a time interval in the same way as that of the controlling object except that the originating alternating current is derived from the control station. These impulses are applied to an input resistance 10c, Fig. 8, the impulses from the control point being applied to a resistance 10b. In the absence of impulses, condensers 8b, 8c are charged and the voltage drop in the anode resistances 5b, 5c of tubes 2b, 2c prevents the discharge in gas-filled tubes 1b, 1c. On the arrival of an impulse at 10b, condenser 8b is discharged via 3b, the current through 5b is reduced and a discharge takes place in 1b. The discharge persists until the arrival of an impulse at 10c, whereupon tube 4b is rendered conducting to charge condenser 8b and so increase the current through 2b. The resulting change in the voltage drop in 5b stops the discharge in 1b. Similarly an impulse applied to 10c causes a discharge in 1c which persists until an impulse is applied to 10b. If the incoming impulses arrive simultaneously, momentary impulses occur in both tubes 1b, 1c, but both condensers 8b and 8c are recharged, increasing the current in 2b and 2c and stopping the discharge in 1b and 1c immediately. Hydraulic servomotor control. The impulses from the anode circuits of the tubes 1b, 1c described in the preceding paragraph may be delivered to magnets 56, 54 controlling the inlet and exhaust valves of a hydraulic motor, Fig. 9, via a reversing switch 44 controlled by the motor. It is arranged that a long impulse applied to a valve magnet makes the magnet more responsive to a subsequent impulse. This is done by making the magnet armature as a movable cylinder containing air and co-operating with a fixed piston through which the air space is in imperfect communication with the pressure fluid. During quiescence, pressure fluid leaks past a needle valve 79, compressing the air in the armature to provide the armature restoring force. When the armature is attracted the pressure in it is increased and a certain amount of fluid, depending on the duration of the impulse, is forced past a valve 78. When the impulse ceases, the armature is restored, but the restoring pressure is now smaller than before and therefore a subsequent impulse operates the valve more quickly. At the dead centre points, an impulse is given to a third magnet 58 which puts the ram cylinder into communication with a chamber 74 containing air under pressure to prevent lock up. In a modification, the valves are servo-operated, the control magnet 88, Fig. 10, admitting fluid to operate a ram 81 which is restored by a spring 80, when the impulse ceases, at a rate that depends on the position of a needle valve 85. In this arrangement also, therefore, the effect of a long impulse is to make the valve more responsive to a subsequent impulse. In another arrangement, Fig. 11, the motor is controlled by valve gear shown at the top of the figure and actuated by rams 81A, 81B which are controlled by a valve arrangement similar to that controlling the motor but actuated by magnets 105, 106. In this arrangement a lever 96 connected to the rams 81A, 81B and normally forced downwardly by a spring 97 controls pairs of valves for forward and reverse movement of the motor. When the controlling and controlled body are in positional agreement and running at a constant speed, the primary'valve gear is not actuated and remains shut, but the secondary valve gear shown in detail remains in the set position and keeps the servomotor running at a constant speed. Other sets of valve gear may be interposed between the primary and final valves. Application to mathematical machines. The position of the signal impulse may be made, e.g. by mechanical arrangements of known kind, to vary with the original magnitude according to any desired law. Multiplication or division may be effected by dividing or multiplying the frequency of the reference impulses while keeping the position of the signal impulse with respect to one end of each time interval measured by the reference impulses the same. Addition and subtraction of the time periods representing two or more variables are effected directly provided that all the periods are related to the same frequency of reference impulses. Differential coefficients with respect to time may be derived by means of the servo apparatus shown in Fig. 11. When a steady state is reached in which the controlling and controlled magnitude are equal and varying uniformly at the same rate, the position of the bar 96 represents the velocity of the variation. Similarly, if a further valve is interposed between the impulse-controlled valve 104 and the valve system 91-99 and the magnitudes are varying with uniform acceleration, the bar 96 of that valve will give a measure of such acceleration. Additional valves will give the values of higher derivatives. Application to the control of a number of spaced guns from a single observation position. The observation post obtains the distance and directions in altitude and azimuth and from these are derived signals representing the logarithmic sine and cosine of the angular observations and the logarithm of the line of sight distance. From these are derived the logarithm of the height of the target above sea level and the logarithms of the distances E or W and N or S of the position. These signals are converted to signals representing ordinary distances and sent to the gun positions where they are corrected for the position of the gun. The speed and acceleration of the target can be derived at the gun positions from these signals and suitable corrections applied. Multiple transmission. This may. be effected with apparatus similar to that shown in Fig. 2 modified to act as a distributer. In each transmitter, the apparatus A1 is not controlled by the variable magnitude but allots the same part of each cycle to the signal concerned.